Analysis of One-step Self-etch Adhesive Systems

Analysis of One-step Self-etch Adhesive SystemsAbstractPurpose To tax the performance of two grammatical cases of maven-step self-etch adherent systems and one type of two-step etch-and-rinse (as a control) by examining the resin- dentine user larboard and assessing the nano-leakage.Materials and Methods Cervical class V cavities were lively in 30 sound human premolars. Two types of one-step self-etch adhesive, G-Bond (GB) and Adper Prompt L-Pop(APL), and one type of two-step etch-and-rinse adhesive, Excite (Ex), were use to bond the composite paying backs. The restored teeth were incubated in weewee at 371 oC for 24 h. Fifteen were subjected to further immersion in 50% ammoniacal property nitrate solution for 24 h and soaked in photo-developing solution for 8 h. All teeth were sectioned across the bonding surface in bucco-lingual direction. The cut surfaces were polished, followed by 6N HCL action for 45s. All surfaces were metal coated before conducting the ultra-morphol ogical observation, employ the Field Emission S burnning Electron Microscope (FE-SEM), to characterize the crossbreed shape and evaluate the nanoleakage.Results A satisfying difference in the thickness of the mark layer was evident between either adhesive systems (ANOVA, pConclusion GB provides a nano-interaction layer at the dentin/adhesive interface that seems to play an important role in minimizing the degree of associated nanoleakage.KeywordsDentin adhesive, interface characterization, nano-leakag, one-step adhesivesIntroductionAlthough gap-free margins at the dentin/restoration interface could be achieved with some adhesive systems utilizing the total-etch technique, Sano et al., have described another pattern of leakage, by observing the penetration of property nitrate along gap-free margins by the aid of either scanning (SEM) or transmission electron microscopy (TEM). Since leakage was found to occur within the nanometer-sized spaces around the collagen fibrils within the hybrid layer, it has been termed nano-leakage1-5.The nano-leakage usually represents suffusion laterally by manner of the hybrid layer and could be the result of the incomplete infiltration of adhesive resin into the demineralized dentin3. This kind of leakage may also countenance the penetration of bacterial products or oral fluids along the interface, which may result in hydrolytic breakdown of either the adhesive resin or collagen within the hybrid layer, thereby compromising the stability of the resin-dentin bond5.In spite of the technique-associated difficulties, previous studies indicated the efficiency of 50% coin nitrate solution in detecting nano-leakage within the hybrid layer3,6,7. However, the acidity of that solution (pH = 3.4-4.5), during long time immersion could induce demineralization around the edges of the restorations, particularly into the partially-demineralized dentin, leading to false positive results7-9. The modified smooth-staining technique was deep suggested to overcome the drawback of flatware nitrate solution. It utilizes 50 wt% ammoniacal silver nitrate having pH measured at 9.5 aiming to eliminate the possibility of dentin dissolution at the hybrid layer10.Although the nano-leakage for various adhesive systems and its influence on bond strength have been evaluated in previous studies11,12. As well as the effect of unlike parameters as thermo-cycling and etching time on nano-leakage, this in vitro study aimed to evaluate the thickness of the interaction layer and nano-leakage of 2 types of one-step adhesive systems and one type of two-step etch-and-rinse (as a control)8,13.The null hypothesis tried and true was that the one-step adhesive system (G-Bond) might offer better adhesion to perdition walls via formation of a nano-interaction zone instead of the traditional hybrid layer.Materials and MethodsThirty sound freshly extracted premolars of patients indicated for orthodontic treatment were collected. The collected teeth were cleaned using the Pro-sonic 300 MTH (Sultan Chemists, Englewood, NJ, USA), and examined to ensure the absence of cracks using a binocular microscope at 20x magnification (Olympus Co., Tokyo, Japan). The selected teeth were stored in deionized peeing that contained antibacterial agent (0.2% sodium azide) for a maximum of 1 month14. victimisation No. 330 bur (Brasseler USA, Savannah, GA, USA) at high speed with copious air/ pissing spray, standardized 2 mm deep class V cavities were prepared at the buccal surfaces 0.5 mm coronal to the cement-enamel junction of all teeth. The prepared margins were all placed in enamel. A metal, buccal-fitted, index was used to guide the away cavity outlines and a rubber stopper hanged to the burs shank has aided in determining the accurate cavity depth. All the prepared cavities were thoroughly rinsed with water system and air- modify before receiving the composite restorations. Table1.shows the description and manufacturers of material s used in this study.Two one-step, self-etch (G-Bond) and (Adper Prompt L-Pop) adhesive systems were used to retain the Tetric Ceram hybrid composite restorations. In addition, 1 two-step, etch-and-rinse (Excite) adhesive system was also selected to serve as control (n= 10 cavities for each). The self-etch adhesive systems were applied to the prepared cavities and left for 10s before air thinning. Curing of both self-etching adhesives was performed by the use of a light-curing device (Hawe-Neos, Gentilino, Switzerland) for 10s. The dentin surfaces of control cavities were etched with 37% phosphoric acid (Ivoclar-Vivadent) for 15s, washed under copious air-water spray, thuslyce the excess water was removed by blotting with a tissue paper leaving the dentin visibly moist. The Excite adhesive was and then applied using a cleanse for 10s and light-cured for 20s after air-drying of the excess material. The cavities were then filled with composite, and cured for 40s before finishing us ing 1000-grit abrasive paper (SAITAC Abrasive, Torino, Italy) in presence of water-cooling. The restored teeth were incubated in distilled water at 371C for 24 h before sectioning and testing have taken place.Assessing the dentin/adhesive interfaceFive premolars from each group were half-sectioned bucco-lingually across the bonding surface with a low-speed diamond saw (model 650, South Bay Technology Inc., CA, USA). The cut surfaces were then lightly finished using a sequence of 600, 800, and 1000-grit abrasive papers (SAITAC Abrasive) in presence of water-cooling followed with light polishing with diamond paste. The samples were then immersed in 6N (mol/L) HCL for 45 seconds then rinsed with distilled water and dried for 24 h at 37C (Binder Incubator, Type B28, Tuttlingen, Germany). The dried samples were sputter coated with gold-palladium (JEOL, JFC, 1100e, Tokyo, Japan.) The dentin/adhesive interface of each sample was then examined using a field emission scanning electron micros cope (FE-SEM) at 30 KV (JEOL, JSM, 5600LV, Tokyo, Japan)14. The thickness of interaction layer was measured in micrometer gauge using a standard microscale calibrated FE-SEMEvaluating the nano-leakageThe root apices of the remaining five teeth of each group were covered with sticky wax (Dentsply DeTrey, Bois Colombes, France), while their inherent surfaces were coated with two layers of nail varnish except for the cervical margin of the restored cavity and 1 mm around. A modified silver staining technique, was used with basic 50wt% ammoniacal silver nitrate (pH=9.5)15. The chemical reagents from which the staining solution was prepared are listed in (table 1).The solution was freshly prepared by turn 25 g of silver nitrate crystals in 25 ml of distilled water. Concentrated (28%) ammonium hydroxide was used to titrate the black solution until it became absolve as ammonium ions complexed the silver into diamine silver (Ag(NH3)2+) ions. This solution was diluted to 50 ml with disti lled water to achieve a 50wt% solution. The teeth were immediately immersed into the freshly-prepared ammoniacal silver nitrate solution in total darkness for 24 h, followed by thorough rinsing with running distilled water for 5 min. The stained teeth were then placed in a photo developing solution for 8 h under fluorescent light to reduce the diamine silver ions into metallic silver grains within the voids along the bonded interfaces2,3. After removal from the developing solution, the teeth were placed under running distilled water for 5 more minutes. The stained teeth were then sectioned and their cut surfaces were finished, polished and acid-treated following the previously mentioned conditions. The measurements of silver penetration were calculated directly on the SEM monitor, using a multi-point measuring device, observing all the internal cavity margin lengths, in steps of approximately 100 m6. The leakage values were expressed as the sum of the cavity margin lengths screenin g silver deposition.A par between these lengths among the three adhesive systems was possible since the dimensions of all cavities were standardized as mentioned before.Statistical analysisThe data were statistically analyse using SPSS statistical package version 10. The data were examined for normal distribution using Kolmogorov-Smirnov test. One way analysis of variance ANOVA was used to comparison the values of the three groups. The Tukeys post hoc analysis was used to confirm the significance of differences detected between the test groups and the control. The test was considered significant when pResultsSEM images representing the adhesive/dentin (A/D) interfaces ( common fig 1-3) revealed a variation in the thickness of the detected interaction layers between the tested adhesive systems. ANOVA indicated significant differences between thickness of interaction layers of tested adhesives (pThese differences were confirmed among the mean values of Ex and GB (Tukeys comparison, pPenetration of silver along the cavity walls was observed in all samples. (Fig.4-6). Table 3 summarizes the results of nanoleakage testing. ANOVA indicated significant differences between the mean values of the sum of the cavity margin lengths showing silver deposition in the tested adhesive systems (psermonFear of bacterial ingress at the restoration/tooth interface and the subsequent caries recurrence has pushed the interest of researchers to assess the adaptation and adhesion of restorative materials against tooth cavity walls. Several studies, had the concern to evaluate the source of adhesive-dentin bond through assessing the interface characterization2,16,17.In vitro study, it is evident that the G-Bond crapd a thinner interaction zone in comparison to those formed with other adhesives (Figs1-3).Both the Ex and APL formed traditional hybrid layers as a result of resin infiltration within the demineralized dentin through the collagen fibrils. However, the demineralization in case of Ex seems to be more deep as a result of longer time of acid contact (30s). This assumption could explain the formation of the thicker hybrid layer17 17. The interface formed by GB looks assorted as the surface of dentin is decalcified only slightly and there is closely no exposure of collagen fibrils. This suggest that functional monomers contained in the bonding material react with hydroxyapatite to form insoluble calcium, forming a thin transitional zone that could be measured in nanometers, so it could be termed a nano-interaction zone with the ability to reduce the risk of bond deterioration18,19.Moreover, evaluating the microleakage and recently the nanoleakage represent important government agency of assessing the incorrect adaptation of materials20. Although the use of silver nitrate stain was effective in detecting the nanoleakage, this in vitro study used the ammoniacal silver nitrate dye because of its efficiency doing the same job and to eliminate the drawba ck of the regular silver nitrate deminerlizing the dentin3,4,10,15.SEM images (Figures 4-6) indicated the presence of nanoleakage in all samples bonded with different systems as manifested by the infiltration of silver ions at the adhesive/dentine interface and in some instances around the collagen fibrils. These findings could be attributed to the effect of resin contraction at the time of its polymerization21. In addition, the indelicate wetting of the resin to dentin and collagen surfaces could exist as a result of the wet nature of dentin tissues and bonding resin viscosity22. The previously nominated factors could create nanogaps between the bonding resin and dentin surfaces. Confirming the same assumption, other researchers have related the occurrence of nanolekage to the presence of landing fields of imperfect resin infiltration, retained water or other solvent, poor polymerization, or phase separation22,23.On the other hand, various degrees of silver penetration and bright ness were evident between samples of different groups indicating different degrees of nanoleakage. This result could be related to the chemical nature of the adhesive systems themselves that is reflected on the expected degree of polymerization shrinkage and the degree of water sorption (dye solution). The recently-marketed adhesive system, G-Bond, includes water and organic solvents in its chemical formula to improve resin infiltration within the wet dentin substrate, as well as nanofiller particles to reduce the outcome of polymerization contraction24.A study by Pashley EL et al., stated that when HEMA is included as a polymerizable solvent for resin monomers, residual water may brook during evaporation as a result of lowering the vapor pressure of water by HEMA25. In previously published TEM observations, pure polymerized HEMA permitted extensive silver impregnation. The authors stated that when HEMA is copolymerized with other resin monomers in the presence of water, it could form hydrogel in the hybrid layer, resulting in additional silver filled patterns in the interfacial layer. In the present study, both APL and Ex. contain HEMA and water which could be the reason of the higher degree of nanoleakage. However the presence of alcohol solvent in the Ex preparedness could improve the resin infiltration and accordingly reduces the degree of nanoleakage in comparison to the solvent-free adhesive APL22,26.ConclusionWithin the limitation of this study, the hypothesis that G-Bond adhesive system can offer better adhesion to cavity walls is acceptable. The formation of a nano-interaction layer seems to play an important role in minimizing the degree of nanoleakage at the bonding interfaceClinical relevance Using the G-Bond adhesive system for bonding composite restorations can minimize the expected degree of nanoleakage and accordingly could reduce the possibility of the future caries recurrence.FiguresFig (1) SEM image of the interface bonded with G-Bond. T he area shown by arrows, between the cured adhesive layer (A) and the dentin (D), is the very thin interaction (hybrid) layer. The electron density in this area is higher than that found with other adhesives.C= composite resin, A= adhesive D= dentinFig (2) SEM image of the interface bonded with Adper Prompt L-Pop. The area shown by arrows, between the cured adhesive layer (A) and the dentin (D), is distinct (hybrid) layer with a uniform thickness than that with G-Bond. The funnel molded configuration of the resin tags is visible, which is resulted by removal of the extremely mineralized peri-tubular dentin.C= composite resin, A= adhesive D= dentinFig (3) SEM image of the interface bonded with Excite. The area shown by arrows, between the cured adhesive layer (A) and the dentin (D), is distinct (hybrid) layer with a uniform thickness than that with G-Bond. The funnel shaped configuration of the resin tags is visible, which is resulted by removal of the highly mineralized peri-tubula r dentin.C= composite resin, A= adhesive D= dentinFig (4) SEM image of the interface bonded with G-Bond showing minimal silver deposition in the form of a small distinct localise area (arrows)C= composite resin, A= adhesive D= dentinFig (5) SEM image of the interface bonded with Adper Prompt L-Pop showing greater and more intense silver deposition in the form of a small distinct localized area (arrows) when compared to G-Bond ( Fig 4) and Excite (Fig 6)C= composite resin, A= adhesive D= dentinFig (6) SEM image of the interface bonded with Excite. The silver deposition presented a less intense pattern when compared to Adper Prompt L-Pop (Fig 5). It was less continuing in the form of a dashed line(arrows) . The silver deposits were mostly located at the stand of hybrid layer, but were sometimes also observed at the top.C= composite resin, A= adhesive D= dentinTablesTable (1) Materials used in the study-CategoriesMaterialsDescriptionCompositionManufacturerI- Adhesive systems1. G-Bond (GB)Self-etch one step no mix adhesivePhosphoric acid ester monomer, UDMA, 4-MET, TEGDMA, Acetone, Water, initiators.GC America, St.Alxip. IL, USA.2. Adper Prompt L-Pop(APL)Self-etch one step no mix adhesiveCompartment 1Methacrylated phosphoric acid esters, photo-initiator, StabilizersCompartment 2Water, HEMA, Polyalkenoic acid, Stabilizers3M ESPE Dental Products, St. Paul, MN, USA.3. Excite(Ex)Etch and rinse adhesiveHEMA,DMA,Phosphoric acid acrylate, highly dispersed silicon dioxide,initiators and Stabilizers in alcohol solution.Ivoclar Vivadent Schaan, Liechtenstien.II- Restorative Materials1. Tetric CeramLight curing, fine particle hybrid resin compositeBisGMA, UDMA, TEGDMA, Ytterbium trifluoride, Barium glass pigments and initiators.Ivoclar VivadentIII- chemical reagents1. Silver nitrate crystalsSigma Chemical Co.St. Louis. MO. USA28% Ammonium hydroxide solutionTable 2 Means and standard deviations of thickness of the interaction layer (m) in tested adhesive systemsAdhesive sys temMeans SD95% confidenceintervalsANOVAP-ValueTurkeysP-ValueG-Bond (GB)0.75 0.160.49 1.00 0.000P1 0.001APL1.65 0.231.56 1.95 0.000P2 0.05Ex (control)2.22 0.231.53 2.50 0.000P1 0.000P1 Turkeys comparison among the means of GB and APL.P2 Turkeys comparison among the means of APL and Ex.P3 Turkeys comparison among the means of GB and Ex.Table 3 Means and standard deviations of the sum of cavity margin lengths (m) showing silver deposition in tested adhesive systemsAdhesive systemMeans SD95% confidenceintervalsANOVAP-ValueTurkeysP-ValueG-Bond (GB)12.70 3.278.76 16.64 0.001P1 0.002APL37.34 6.5628.83 45.85 0.001P2 0.05Ex (control)20.74 5.0914.49 26.99 0.001P1 0.05P1 Turkeys comparison among the means of GB and APL.P2 Turkeys comparison among the means of APL and Ex.P3 Turkeys comparison among the means of GB and Ex.